Detergent compositions include nowadays a complex combination of active ingredients which fulfill certain specific needs: a surfactant system, enzymes providing cleaning and fabric care benefits, bleaching agents, a builder system, suds suppressors, soil-suspending agents, soil-release agents, optical brighteners, softening agents, dispersants, dye transfer inhibition compounds, abrasives, bactericides, perfumes, and their overall performance has indeed improved over the years. In particular, current detergent formulations generally include detergent enzymes and more specifically cellulases.
The activity of cellulase is one in which cellulosic fibres or substrates are hydrolysed by the cellulase and depending on the particular function of the cellulase, which can be endo- or exo-cellulase and the respective hemicellulases. The cellulose structures are depolymerized or cleaved into smaller and thereby more soluble or dispersible fractions. This activity in particular on fabrics provides a cleaning, rejuvenation, softening and generally improved handfeel characteristics to the fabric structure.
The efficiency of cellulytic enzymes, i.e. cellulases, in terms of textile cleaning and harshness-reducing agent for fabrics has been recognized for some time; Wo 89/09259, GB-A-2,075,028, GB-A-2,095,275 and GB-A-2,094,826, disclose detergent compositions with cellulase for improved cleaning performance; GB-A-1,368,599 discloses the use of cellulase for reducing the harshness of cotton-containing fabrics; U.S. Pat. No. 4,435,307 teaches the use of a cellulytic enzyme derived from Humicola insolens as well as a fraction thereof, designated ACXI, as a harshness-reducing detergent additive.
EP-A-0 269 168 discloses optimized detergent compositions containing cellulase, which are formulated at a mild alkaline pH range and provide combined fabric cleaning, fabric softening, and fabric care performance.
Specific cellulases suitable for the present invention have been described in WO91/17244 wherein single-component enzymes selected for high specific activity are described and wherein an enzyme capable of degrading cellulose or hemicellulose is disclosed.
Also suitable are the cellulolytic enzymes covered in W095/02675 which describes a detergent composition comprising two cellulase components : a first cellulase component having a retaining-type activity and being capable of particulate soil removal and a second cellulase component having multiple domains comprising at least one non-catalytical domain attached to a catalytic domain and being capable of colour clarification wherein at least one of the cellulase components is a single component. Said enzymatic detergent composition is capable of providing both sufficient colour clarification and particulate soil removal which, after a limited number of washing cycles, neither damage nor partly degrade the cellulose-containing fabric.
Suitable cellulases are the EGIII cellulases from Trichoderma longibrachiatum described in WO94/21801, Genencor, published Sep. 29, 1994.
Current granular bleach-containing laundry detergent compositions possess a pH 1% solution of about 10.5 allowing maximum bleach performance via optimum perhydrolysis obtained at said pH. The cleaning performance of such bleach-containing laundry detergent compositions is known to diminish with the reduction of pH. A lower pH is nevertheless necessary to obtain full enzymatic performance of cellulase containing detergents.
It is therefore an object of the present invention to formulate a granular bleach-containing laundry detergent composition combining the cleaning benefits of the bleaching agents together with the enzymatic cleaning performance of cellulase in order to provide superior cleaning and whiteness performance benefits.
It has been surprisingly found that granular bleach-containing laundry detergent compositions comprising a specific cellulase and having a 1% solution pH between 7.5 and 10, provide optimum cleaning and whiteness performance benefits.
Indeed, it is believed that said optimised pH enhances the specific cellulase performance while not drastically reducing the bleach cleaning and whiteness performance benefits. The slight reduction in cleaning performance due to a slight reduction in the perhydrolysis rate is compensated with an increased enzymatic performance and a reduced darkening of the bleach sensitive stains at lower pH.